Reactivity and models for anion distribution: specific iodide binding to sulfobetaine micelles.
The reaction of I (-) with methyl naphthalene-2-sulfonate (MeONs) is accelerated by the micellized sulfobetaine surfactants N-decyl, N-dodecyl, N-tetradecyl, and N-hexadecyl- N, N-dimethylammonio-1-propanesulfonate. Concentrations of micellar-bound I (-) were determined by using ion-selective electrodes (ISE), and capillary electrophoresis. At low concentrations, I (-) incorporation fits Langmuir isotherms and is related to changes in micellar surface potentials. Rate effects of dilute KI are fitted quantitatively by a pseudophase model that describes I (-) binding in terms of a sorption isotherm, but at higher [KI], where the simple model predicts saturation, rates increase due to electrolyte invasion. This model considers transfer equilibria of both reactants between water and micelles and second-order rate constants in each pseudophase. Estimated second-order rate constants for reaction of MeONs with I (-) in the micellar pseudophase are 3.2- to 3.5-fold higher than the second-order rate constant, k 2w, in water, depending on surfactant structure and assumptions in the treatment.
Farrukh
M Akhyar
MA
Departamento de Quimica, Universidade Federal de Santa Catarina, Florianopolis, Santa Catarina 88040-900, Brazil. faruk@qmc.ufsc.br
Beber
Rosane C
RC
Priebe
Jacks P
JP
Lal Satnami
Manmohan
M
Micke
Gustavo A
GA
Costa
Ana C O
AC
Fiedler
Haidi D
HD
Bunton
Clifford A
CA
Nome
Faruk
F